The present disclosure relates to a carrier head and a carrier head unit, and more particularly, to a carrier head and a carrier head unit for sucking and securely supporting a substrate during a chemical mechanical polishing process.
As semiconductor integrated circuits are miniaturized and have a multi-layer structure, a surface of wafers is planarized in a certain semiconductor fabrication process, or a conductive layer is selectively removed from a surface of wafers. To this end, a chemical mechanical polishing (CMP) process is widely used. Recently, as a metal interconnection process is performed using a combination of a chemical mechanical polishing method and a dual damascene method, the chemical mechanical polishing process is becoming increasingly important.
When a semiconductor device is fabricated, a chemical mechanical polishing (CMP) system may perform a global planarization process on a wafer to decrease surface roughness caused by repeated masking, etching, and interconnection processes, thereby removing height differences between a cell region and a peripheral circuit region. In addition, a chemical mechanical polishing system may precisely polish a surface of a wafer to decrease surface roughness caused by a high integrated device fabrication process and a contact/interconnection layer isolation process for forming a circuit.
In a typical chemical mechanical polishing process, slurry is applied to a polishing pad, and a wafer is pressed. In this state, the polishing pad and the wafer are relatively rotated to planarize a surface of the wafer or selectively remove a conductive layer. That is, the polishing pad is used as a mechanical component, and the slurry is used as a chemical component, thereby mechanically and chemically polishing a surface of a wafer.
During a chemical mechanical polishing process, a carrier head applies polishing pressure to a wafer, and rotates the wafer. Further, a carrier head may transfer a wafer. A main body of such a carrier head is provided with a retaining ring that surrounds the side surface of a wafer to prevent a dislocation of the wafer due to a rotational motion.
The retainer ring is coupled to the main body of the carrier head by coupling members such as bolts. The coupling members may be loosen by a vibration due to rotations of the carrier head and the polishing pad during the chemical mechanical polishing process. Accordingly, the retainer ring may be spaced apart or removed from the main body. In this case, the wafer may be improperly supported, or be removed from the carrier head, and thus, the chemical mechanical polishing process should be stopped. Furthermore, the wafer and the carrier head may be damaged.